package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MapperStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * @author YiYa
 * @since 2020-11-08 下午 04:07
 */
public class SimpleExecutor implements Executor {
    @Override
    public <E> List<E> query(Configuration configuration, MapperStatement mapperStatement, Object... params) throws Exception {
        // 1、注册对象， 获取连接
        Connection connection = configuration.getDataSource().getConnection();
        // 2、获取SQL语句并转换
        String sql = mapperStatement.getSql();
        // 绑定
        BoundSql boundSql = getBoundSql(sql);

        // 3、获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        // 4、 设置参数
        String parameterType = mapperStatement.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappings();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            // 反射
            Field declaredField = parameterTypeClass.getDeclaredField(content);
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i + 1, o);
        }

        // 5、执行SQL
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mapperStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        ArrayList<Object> objects = new ArrayList<>();

        // 6、封装返回结果集
        while (resultSet.next()) {
            Object o = resultTypeClass.newInstance();
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                // 字段名
                String columnName = metaData.getColumnName(i);
                // 字段值
                Object value = resultSet.getObject(columnName);
                //  使用反射或内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method method = propertyDescriptor.getWriteMethod();
                method.invoke(o, value);
            }
            objects.add(o);
        }
        return (List<E>) objects;
    }

    @Override
    public Integer insert(Configuration configuration, MapperStatement mapperStatement, Object... params) throws Exception {
        // 1、注册对象， 获取连接
        Connection connection = configuration.getDataSource().getConnection();
        // 2、获取SQL语句并转换
        String sql = mapperStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);
        // 3、获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        // 4、 设置参数
        String parameterType = mapperStatement.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappings();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            // 反射
            Field declaredField = parameterTypeClass.getDeclaredField(content);
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i + 1, o);
        }
        // 5、执行SQL
        int insert = preparedStatement.executeUpdate();
        return insert;
    }

    @Override
    public Integer update(Configuration configuration, MapperStatement mapperStatement, Object... params) throws Exception {
        // 1、注册对象， 获取连接
        Connection connection = configuration.getDataSource().getConnection();
        // 2、获取SQL语句并转换
        String sql = mapperStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);
        // 3、获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        // 4、 设置参数
        String parameterType = mapperStatement.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappings();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            // 反射
            Field declaredField = parameterTypeClass.getDeclaredField(content);
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i + 1, o);
        }
        // 5、执行SQL
        int update = preparedStatement.executeUpdate();
        return update;
    }

    @Override
    public Integer delete(Configuration configuration, MapperStatement mapperStatement, Object... params) throws Exception {
        // 1、注册对象， 获取连接
        Connection connection = configuration.getDataSource().getConnection();
        // 2、获取SQL语句并转换
        String sql = mapperStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);
        // 3、获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        // 4、 设置参数
        String parameterType = mapperStatement.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappings();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            // 反射
            Field declaredField = parameterTypeClass.getDeclaredField(content);
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i + 1, o);
        }
        // 5、执行SQL
        int delete = preparedStatement.executeUpdate();
        return delete;
    }

    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if(parameterType!=null){
            Class<?> aClass = Class.forName(parameterType);
            return aClass;
        }
        return null;
    }

    /**
     * 将#{}与?进行替换，将#{}里的值进行存储
     * @param sql sql语句
     * @return 结果
     */
    private BoundSql getBoundSql(String sql) {
        // 标记处理器: 配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler params = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", params);
        // 解析后的SQL
        String parseSql = genericTokenParser.parse(sql);
        // #{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = params.getParameterMappings();

        return new BoundSql(parseSql, parameterMappings);
    }
}
